Methods for coherent antenna switching in AoD positioning scheme

ABSTRACT

Devices and methods of estimating the AoD of a STA are generally described. The STA receives comparison symbols from a first AP antenna. The comparison symbols are received prior to and after switching of transmitter chains from a first set of antennas to a second set of antennas. AoD symbols are received immediately after the comparison symbols. A phase and amplitude correction is determined based on a phase and amplitude change between the comparison symbols and the second AoD symbol corrected based thereon. The AoD is subsequently estimated based on the symbol measurements.

PRIORITY CLAIM

This application claims the benefit of priority to U.S. ProvisionalPatent Application Ser. No. 62/281,345, filed Jan. 21, 2016, andentitled “APPARATUS, SYSTEM AND METHOD OF ANGLE OF DEPARTURE (AOD)ESTIMATION,” and U.S. Provisional Patent Application Ser. No.62/299,692, filed Feb. 25, 2016, and entitled “A METHOD OF USING LOWPOWER WAKE-UP RADIO FOR SERVICE DISCOVERY,” which are incorporatedherein by reference in their entirety.

TECHNICAL FIELD

Embodiments pertain to wireless networks. Some embodiments relate towireless local area networks (WLANs) and Wi-Fi networks includingnetworks operating in accordance with the Institute of Electrical andElectronics Engineers (IEEE) 802.11 family of standards, such as theIEEE 802.11ac standard, the IEEE 802.11ax study group (SG) (namedDensiFi) or IEEE 802.11 ay or IEEE 802.11az. Some embodiments relate toWiFi positioning of a station (STA).

BACKGROUND

The use of mobile communication devices (also referred to as stations(STAs)) continues to increase among all walks of modem society. Thevarious uses and capabilities of STAs has continued to drive demand fora wide variety of networked STAs in a number of disparate environments.Many applications use aspects of the STA characteristics, such as theincreasing processing ability and screen size, as well as environmentalconditions to expand use at home and work. One of the most popularenvironmental conditions employed by applications and advertisers is STAlocation. In one particular, example the use of Angle of Departure (AoD)techniques may he to determine STA position. However, a number of issuesremain with the equipment and accuracy used in AoD techniques.

BRIEF DESCRIPTION OF THE FIGURES

In the figures, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The figures illustrate generally, by way of example, but notby way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 is a functional diagram of a wireless network in accordance withsome embodiments.

FIG, 2 illustrates components of a communication device in accordancewith some embodiments.

FIG. 3 illustrates a block diagram of a communication device inaccordance with some embodiments.

FIG. 4 illustrates another block diagram of a communication device inaccordance with some embodiments.

FIG. 5 illustrates a transmission from an access point (AP) at Angle ofDeparture (AoD) in accordance with some embodiments.

FIG. 6 is a calibration method transmission from an AP in accordancewith some embodiments.

FIG. 7 is another calibration method transmission from an AP inaccordance with some embodiments.

FIG. 8 is a relative phase method transmission from an AP in accordancewith some embodiments.

FIG, 9 illustrates a method of determining AoD in accordance with someembodiments.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass all available equivalentsof those claims.

FIG. 1 illustrates a wireless network in accordance with someembodiments. Elements in the network 100 may engage in channel bonding,as described herein. In some embodiments, the network 100 may be anEnhanced Directional Multi Gigabit (EDMG) network. In some embodiments,the network 100 may be a High Efficiency Wireless Local Area Network(FIE) network. In some embodiments, the network 100 may be a WirelessLocal Area Network (WLAN) or a Wi-Fi network. These embodiments are notlimiting, however, as some embodiments of the network 100 may include acombination of such networks. As an example, the network 100 may supportEDMG devices in some cases, non EDMG devices in some cases, and acombination of EDMG devices and non EDMG devices in some cases. Asanother example, the network 100 may support HE devices in some cases,non HE devices in some cases, and a combination of HE devices and non HEdevices in some cases. As another example, some devices supported by thenetwork 100 may be configured to operate according to EDMG operationand/or HE operation and/or legacy operation. Accordingly, it isunderstood that although techniques described herein may refer to a nonEDMG device, an EDMG device, a non FIE device or an HE device, suchtechniques may be applicable to any or all such devices in some cases.

The network 100 may include any number (including zero) of masterstations (STA) 102, user stations (STAs) 103 (legacy STAs), HE stations104 (HE devices), and EDMG stations 105 (EDMG devices). It should benoted that in some embodiments, the master station 102 may be astationary non-mobile device, such as an access point (AP). In sonicembodiments, the STAs 103 may be legacy stations. These embodiments arenot limiting, however, as the STAs 103 may be FIE devices or may supportHE operation in some embodiments. In some embodiments, the STAs 103 maybe EDMG devices or may support EDMG operation. It should be noted thatembodiments are not limited to the number of master STAs 102, STAs 103,HE stations 104 or EDMG stations 105 shown in the example network 100 inFIG. 1. Legacy STAs 103 may include, for example, non-HT STA (e.g., IEEE802.11a/g stations), HT STA (e.g., IEEE 802.11n stations), and VHT STA(e.g., IEEE 802.11ac stations).

The master station 102 may be arranged to communicate with the STAs 103and/or the HE STAs 104 and/or the EDMG STAs 105 in accordance with oneor more of the IEEE 802.11 standards. In accordance with someembodiments, an AP may operate as the master station 102 and may bearranged to contend for a wireless medium (e.g., during a contentionperiod) to receive exclusive control of the medium for a. HE controlperiod (i.e., a. transmission opportunity (TXOP)). The master station102 may, for example, transmit a master-sync or control transmission atthe beginning of the HE control period to indicate, among other things,which HE stations 104 are scheduled for communication during the HEcontrol period. During the HE control period, the scheduled HE stations104 may communicate with the master station 102 in accordance with anon-contention based multiple access technique. In some embodiments, theSTAs 103 may communicate in accordance with a contention-basedcommunication technique, rather than a non-contention based multipleaccess technique. During the HE control period, the master station 102may communicate with HE stations 104 using one or more HE frames. Duringthe HE control period, STAs 103 not operating as HE devices may refrainfrom communicating in some cases. In some embodiments, the master-synctransmission may be referred to as a control and schedule transmission.

In some embodiments, the multiple-access technique used during the HEcontrol period may be a scheduled orthogonal frequency division multipleaccess (OFDMA) technique, although this is not a requirement. In someembodiments, the multiple access technique may be a time-divisionmultiple access (TDMA) technique or a frequency division multiple access(TDMA) technique. In some embodiments, the multiple access technique maybe a space-division multiple access (SDMA) technique including amulti-user (MU) multiple-input multiple-output (MIMO) (MU-MIMO)technique. These multiple-access techniques used during the HE controlperiod may be configured for uplink or downlink data communications.

The master station 102 may also communicate with STAs 103 and/or otherlegacy stations in accordance with legacy IEEE 802.11 communicationtechniques. In some embodiments, the master station 102 may also beconfigurable to communicate with the HE stations 104 outside the HEcontrol period in accordance with legacy IEEE 802.11 communicationtechniques, although this is not a requirement.

In some embodiments, the HE communications during the HE control periodmay be configurable to use one of 20 MHz, 40 MHz, or 80 MHz contiguousbandwidths or an 80+80 MHz (160 MHz) non-contiguous bandwidth. In someembodiments, a 320 MHz channel width may be used. In some embodiments,subchannel bandwidths less than 20 MHz may also be used, in theseembodiments, each channel or subchannel (or tone) of an HE communicationmay be configured for transmitting a number of spatial streams.

In some embodiments, EDMG communication may be configurable to usechannel resources that may include one or more frequency bands of 2.16GHz, 4.32 GHz or other bandwidth. Such channel resources may or may notbe contiguous in frequency. As a non-limiting example, EDMGcommunication may be performed in channel resources at or near a carrierfrequency of 60 GHz.

In some embodiments, primary channel resources may include one or moresuch bandwidths, which may or may not be contiguous in frequency. As anon-limiting example, channel resources spanning a 2.16 GHz or 4.32 GHzbandwidth may be designated as the primary channel resources. As anothernon-limiting example, channel resources spanning a 20 MHz bandwidth maybe designated as the primary channel resources. In some embodiments,secondary channel resources may also be used, which may or may not becontiguous in frequency. As a non-limiting example, the secondarychannel resources may include one or more frequency bands of 2.16 GHzbandwidth, 4.32 GHz bandwidth or other bandwidth. As anothernon-limiting example, the secondary channel resources may include one ormore frequency bands of 20 MHz bandwidth or other bandwidth.

In some embodiments, the primary channel resources may be used fortransmission of control messages, beacon frames or other frames orsignals by the AP 102. As such, the primary channel resources may be atleast partly reserved for such transmissions. In some cases, the primarychannel resources may also be used for transmission of data payloadsand/or other signals. In some embodiments, the transmission of thebeacon frames may be restricted such that the AP 102 does not transmitbeacons on the secondary channel resources. Accordingly, beacontransmission may be reserved for the primary channel resources and maybe restricted and/or prohibited in the secondary channel resources, insome cases.

In accordance with some embodiments, a master station 102 and/or HEstations 104 may generate an HE packet in accordance with a shortpreamble format or a long preamble format. The HE packet may comprise alegacy signal field (L-SIG) followed by one or more high-efficiency (HE)signal fields (HE-SIG) and an HE long-training field (HE-LTF). For theshort preamble format, the fields may be configured for shorter-delayspread channels. For the long preamble format, the fields may beconfigured for longer-delay spread channels. These embodiments aredescribed in more detail below.

In some embodiments, channel bonding may be used in communicationsbetween the various devices, for example, the STAs 103. In channelbonding, two or more channels may be used simultaneously, e.g., in thesame physical layer (PHY) packet to achieve higher throughput. Due tothe directional nature of transmissions in the 60GHz hand, to usechannel bonding a clear channel may he assessed before transmission.Thus, both sides of a particular link, i.e., the TXOP initiator and theTXOP responder, may assess the clear channel prior to transmission.Every wideband transmission opportunity may start with a Request to Send(RTS) and a Clear to Send (CTS) (RTS/CTS) protocol.

For example, a STA 103 may transmit a RTS message to the AP 102. After aShort Inter Frame Space (SIFS) period, if the medium is available, theAP 102 may respond to the RTS by broadcasting a CTS message. After theCTS message is received by the STA 103, the STA 103 may wait until abackoff counter reaches zero. The STA 103 may then transmit the datapacket to the AP 102 during the TXOP. If the medium becomes busy beforethe backoff counter reaches zero, the STA 103 may sense when the mediumagain becomes available and transmit another RTS message to the AP 102.

After each transmission, the STA 103 may pick a new backoff time.Assuming the STA 103 received an acknowledgment (ACK) from the AP 102indicating reception of the packet by the AP 102, if the backoff counterexpires before the next packet arrives for transmission, the STA 103 cantransmit after sensing the channel to be idle for the DIFS period. Ifthe last transmission was unsuccessful, as evidenced by the lack ofreception of the ACK by the STA 103, the STA 103 may wait for anExtended Inter Frame Space (EIFS) period, which is longer than the DIFSperiod. If the STA 103 has a data packet waiting for transmission andthe backoff counter expires, but the carrier sensing detects that thecarrier is occupied, the STA 103 may select a second backoff time forthe backoff counter and transmit the packet when the second backoff timehas expired.

In some embodiments, STAs may use a Short Inter Frame Space (SIFS) forthe RTS/CTS message and for a positive ACK-based high prioritytransmission. Once the SIFS duration elapses, the transmission canimmediately start. Depending on the physical layer configuration, theSITS duration may be 6, 10 or 28 μs. A PCF Inter Frame Space (PITS) maybe used by the PCF during contention free operations. After the PIFSperiod elapses, STAs having data to be transmitted in contention freeperiod can be initiated, preempting contention based traffic. The DIESperiod is the minimum idle time for contention based services. STAs mayaccess the channel immediately if it is free after the DIFS period. TheEIFS period may be used, as above, when there is erroneous frametransmission. The Arbitration Inter Frame Space period (AIFS) may beused by QoS STAs to transmit all frames (data and control).

In particular, the CCA process may be performed by the physical layer.The physical layer can be divided into two sublayers. The sublayers mayinclude the physical medium dependent (PMD, lower sublayer) and thephysical layer convergence procedure (PLCP, upper sublayer). Thephysical layer may determine whether the channel is clear andcommunicate this to the MAC layer. The PMD may indicate to the PLCPsublayer whether the medium is in use. The PLCP sublayer may communicatewith the MAC layer to indicate a busy or idle medium, which may preventthe MAC layer from attempting* to forward a frame for transmission. CCA,may include both energy detection (ED) and CS. For the CS CCA process,the STA 103 may detect and decode a WiFi preamble from the PLCP headerfield. For the ED CCA process, the STA 103 may detect non-WiFi energy inthe operating channel and backoff data transmission. The ED thresholdmay be dependent in some embodiments on the channel width. If thenon-WiFi energy exceeds the ED threshold for a predetermined amount oftime, the STA 103 may determine that the medium is busy until the energyis below the threshold.

FIG. 2 illustrates components of a communication device in accordancewith some embodiments. The communication device 200 may be one of theUEs 102a or STAs 103 or some other network component. The communicationdevice 200 may be a stationary, non-mobile device or may be a mobiledevice. In some embodiments, the UE 200 may include applicationcircuitry 202, baseband circuitry 204, Radio Frequency (RF) circuitry206, front-end module (FEM) circuitry 208 and one or more antennas 210,coupled together at least as shown. At least some of the basebandcircuitry 204, RF circuitry 206, and FEM circuitry 208 may form atransceiver. In some embodiments, other network elements, such as an eNBor AP may contain some or all of the components shown in FIG. 2.

The application or processing circuitry 202 may include one or moreapplication processors. For example, the application circuitry 202 mayinclude circuitry such as, but not limited to, one or more single-coreor multi-core processors. The processor(s) may include any combinationof general-purpose processors and dedicated processors(e.g., graphicsprocessors, application processors, etc.). The processors may be coupledwith and/or may include memory/storage and may be configured to executeinstructions stored in the memory/storage to enable various applicationsand/or operating systems to run on the system.

The baseband circuitry 204 may include circuitry such as, but notlimited to, one or more single-core or multi-core processors. Thebaseband circuitry 204 may include one or more baseband processorsand/or control logic to process baseband signals received from a receivesignal path of the RF circuitry 206 and to generate baseband signals fora transmit signal path of the RF circuitry 206. Baseband processingcircuitry 204 may interface with the application circuitry 202 forgeneration and processing of the baseband signals and for controllingoperations of the RF circuitry 206. For example, in sonic embodiments,the baseband circuitry 204 may include a second generation (2G) basebandprocessor 204 a, third generation (3G) baseband processor 204 b, fourthgeneration (4G) baseband processor 204 c, and/or other basebandprocessor(s) 204 d for other existing generations, generations indevelopment or to be developed in the future (e.g., fifth generation(5G), 5G, etc). The baseband circuitry 204 (e.g., one or more ofbaseband processors 204 a-d) may handle various radio control functionsthat enable communication with one or more radio networks via the RFcircuitry 206. The radio control functions may include, but are notlimited to, signal modulation/demodulation, encoding/decoding, radiofrequency shifting, etc. In some embodiments, modulation/demodulationcircuitry of the baseband circuitry 204 may include FFT, precoding,and/or constellation mapping/demapping functionality. In someembodiments, encoding/decoding circuitry of the baseband circuitry 204may include convolution, tail-biting convolution, turbo, Viterbi, and/orLow Density Parity Check (LDPC) encoder/decoder functionality.Embodiments of modulation/demodulation and encoder/decoder functionalityare not limited to these examples and may include other suitablefunctionality in other embodiments.

In some embodiments, the baseband circuitry 204 may include elements ofa protocol stack such as, for example, elements of an EUTRAN protocolincluding, for example, physical (PHY), media access control (MAC),radio link control (RLC), packet data convergence protocol (PDCP),and/or radio resource control (RRC) elements. A central processing unit(CPU) 204 e of the baseband circuitry 204 may be configured to runelements of the protocol stack for signaling of the PHY, MAC, RLC, PDCPand/or RRC layers. In some embodiments, the baseband circuitry mayinclude one or more audio digital signal processor(s) (DSP) 204 f. Theaudio DSP(s) 204 f may be include elements for compression/decompressionand echo cancellation and may include other suitable processing elementsin other embodiments. Components of the baseband circuitry may besuitably combined in a single chip, a single chipset, or disposed on asame circuit board in some embodiments. In some embodiments, some or allof the constituent components of the baseband circuitry 204 and theapplication circuitry 202 may be implemented together such as, forexample, on a system on a chip (SOC).

In some embodiments, the baseband circuitry 204 may provide forcommunication compatible with one or more radio technologies. Forexample, in some embodiments, the baseband circuitry 204 may supportcommunication with an EUTRAN and/or other wireless metropolitan areanetworks (WMAN), a wireless local area network (WLAN), a wirelesspersonal area network (WPAN). Embodiments in which the basebandcircuitry 204 is configured to support radio communications of more thanone wireless protocol may be referred to as multi-mode basebandcircuitry. In some embodiments, the device can be configured to operatein accordance with communication standards or other protocols orstandards, including Institute of Electrical and Electronic Engineers(IEEE) 802.16 wireless technology (WiMax), IEEE 802.11 wirelesstechnology (WiFi) including IEEE 802.11 ad, which operates in the 60 GHzmillimeter wave spectrum, various other wireless technologies such asglobal system for mobile communications (GSM), enhanced data rates forGSM evolution (EDGE), GSM EDGE radio access network (GERAN), universalmobile telecommunications system (UMTS), UMTS terrestrial radio accessnetwork (UTRAN), or other 2G, 3G, 4G, 5G, etc. technologies eitheralready developed or to be developed.

RF circuitry 206 may enable communication with wireless networks usingmodulated electromagnetic radiation through a non-solid medium. Invarious embodiments, the RF circuitry 206 may include switches, filters,amplifiers, etc. to facilitate the communication with the wirelessnetwork. RF circuitry 206 may include a receive signal path which mayinclude circuitry to down-convert RF signals received from the FEMcircuitry 208 and provide baseband signals to the baseband circuitry204. RF circuitry 206 may also include a transmit signal path which mayinclude circuitry to up-convert baseband signals provided by thebaseband circuitry 204 and provide RF output signals to the FEMcircuitry 208 for transmission.

In some embodiments, the RF circuitry 206 may include a receive signalpath and a transmit signal path. The receive signal path of the RFcircuitry 206 may include mixer circuitry 206 a, amplifier circuitry 206b and filter circuitry 206 c. The transmit signal path of the RFcircuitry 206 may include filter circuitry 206 c and mixer circuitry 206a. RF circuitry 206 may also include synthesizer circuitry 206 d forsynthesizing a frequency for use by the mixer circuitry 206 a of thereceive signal path and the transmit signal path. In some embodiments,the mixer circuitry 206 a of the receive signal path may be configuredto down-convert RF signals received from the FEM circuitry 208 based onthe synthesized frequency provided by synthesizer circuitry 206 d Theamplifier circuitry 206 b may be configured to amplify thedown-converted signals and the filter circuitry 206 c may be a low-passfilter (LPF) or band-pass filter (BPF) configured to remove unwantedsignals from the down-converted signals to generate output basebandsignals. Output baseband signals may be provided to the basebandcircuitry 204 for further processing. In some embodiments, the outputbaseband signals may be zero-frequency baseband signals, although thisis not a requirement. In some embodiments, mixer circuitry 206 a of thereceive signal path may comprise passive mixers, although the scope ofthe embodiments is not limited in this respect.

In some embodiments, the mixer circuitry 206 a of the transmit signalpath may be configured to up-convert input baseband signals based on thesynthesized frequency provided by the synthesizer circuitry 206 d togenerate RF output signals for the FEM circuitry 208. The basebandsignals may be provided bye the baseband circuitry 204 and may befiltered by filter circuitry 206 c. The filter circuitry 206 c mayinclude a low-pass filter (LPF), although the scope of the embodimentsis not limited in this respect.

in some embodiments, the mixer circuitry 206 a of the receive signalpath and the mixer circuitry 206 a of the transmit signal path mayinclude two or more mixers and may be arranged for quadraturedownconversion and/or upconversion respectively. In some embodiments,the mixer circuitry 206 a of the receive signal path and the mixercircuitry 206 a of the transmit signal path may include two or moremixers and may be arranged for image rejection (e.g., Hartley imagerejection). In some embodiments, the mixer circuitry 206 a of thereceive signal path and the mixer circuitry 206 a may be arranged fordirect downconversion and/or direct upconversion, respectively. In someembodiments, the mixer circuitry 206 a of the receive signal path andthe mixer circuitry 206 a of the transmit signal path may be configuredfor super-heterodyne operation.

In some embodiments, the output baseband signals and the input basebandsignals may be analog baseband signals, although the scope of theembodiments is not limited in this respect. In some alternateembodiments, the output baseband signals and the input baseband signalsmay be digital baseband signals. In these alternate embodiments, the RFcircuitry 206 may include analog-to-digital converter (ADC) anddigital-to-analog converter (DAC) circuitry and the baseband circuitry204 may include a digital baseband interface to communicate with the RFcircuitry 206.

In some dual-mode embodiments, a separate radio IC circuitry may beprovided for processing signals for each spectrum, although the scope ofthe embodiments is not limited in this respect.

In some embodiments, the synthesizer circuitry 206 d may be afractional-N synthesizer or a fractional N/N+1 synthesizer, although thescope of the embodiments is not limited in this respect as other typesof frequency synthesizers may be suitable. For example, synthesizercircuitry 206 d may be a delta-sigma synthesizer, a frequencymultiplier, or a synthesizer comprising a phase-locked loop with afrequency divider.

The synthesizer circuitry 206 d may be configured to synthesize anoutput frequency for use by the mixer circuitry 206 a of the RFcircuitry 206 based on a frequency input and a divider control input. Insome embodiments, the synthesizer circuitry 206 d may be a fractionalN/N+1 synthesizer.

In some embodiments, frequency input may be provided by a voltagecontrolled oscillator (VCO), although that is not a requirement. Dividercontrol input may be provided by either the baseband circuitry 204 orthe applications processor 202 depending on the desired outputfrequency. In some embodiments, a divider control input (e.g., N) may bedetermined from a look-up table based on a channel indicated by theapplications processor 202.

Synthesizer circuitry 206 d of the RF circuitry 206 may include adivider, a delay-locked loop (DLL), a multiplexer and a phaseaccumulator. In some embodiments, the divider may be a dual modulusdivider (DMD) and the phase accumulator may be a digital phaseaccumulator (DPA). In some embodiments, the DMD may be configured todivide the input signal by either N or N+1 (e.g., based on a carry out)to provide a fractional division ratio. In some example embodiments, theDLL may include a set of cascaded, tunable, delay elements, a phasedetector, a charge pump and a D-type flip-flop. In these embodiments,the delay elements may be configured to break a VCO period up into Ndequal packets of phase, where Nd is the number of delay elements in thedelay line. In this way, the DLL provides negative feedback to helpensure that the total delay through the delay line is one VCO cycle.

In some embodiments, synthesizer circuitry 206 d may be configured togenerate a carrier frequency as the output frequency, while in otherembodiments, the output frequency may be a multiple of the carrierfrequency (e.g., twice the carrier frequency, four times the carrierfrequency) and used in conjunction with quadrature generator and dividercircuitry to generate multiple signals at the carrier frequency withmultiple different phases with respect to each other. In someembodiments, the output frequency may be a LO frequency (f_(LO)). Insome embodiments, the RF circuitry 206 may include an IQ/polarconverter.

FEM circuitry 208 may include a receive signal path which may includecircuitry configured to operate on RF signals received from one or moreantennas 210, amplify the received signals and provide the amplifiedversions of the received signals to the RF circuitry 206 for furtherprocessing. FEM circuitry 208 may also include a transmit signal pathwhich may include circuitry configured to amplify signals fortransmission provided by the RF circuitry 206 for transmission by one ormore of the one or more antennas 210.

In some embodiments, the FEM circuitry 208 may include a TX/RX switch toswitch between transmit mode and receive mode operation. The FEMcircuitry may include a receive signal path and a transmit signal path.The receive signal path of the FEM circuitry may include a low-noiseamplifier (LNA) to amplify received. RF signals and provide theamplified received RF signals as an output (e.g., to the RF circuitry206). The transmit signal path of the FEM circuitry 208 may include apower amplifier (PA) to amplify input RF signals (e.g., provided by RFcircuitry 206), and one or more filters to generate RF signals forsubsequent transmission (e.g., by one or more of the one or moreantennas 210.

In some embodiments, the communication device 200 may include additionalelements such as, for example, memory/storage, display, camera, sensor,and/or input/output (I/O) interface as described in more detail below.In some embodiments, the communication device 200 described herein maybe part of a portable wireless communication device, such as a personaldigital assistant (PDA), a laptop or portable computer with wirelesscommunication capability, a web tablet, a wireless telephone, asmartphone, a wireless headset, a pager, an instant messaging device, adigital camera, an access point, a television, a medical device (e.g., aheart rate monitor, a blood pressure monitor, etc.), or other devicethat may receive and/or transmit information wirelessly. In someembodiments, the communication device 200 may include one or more userinterfaces designed to enable user interaction with the system and/orperipheral component interfaces designed to enable peripheral componentinteraction with the system. For example, the communication device 200may include one or more of a keyboard, a keypad, a touchpad, a display,a sensor, a non-volatile memory port, a universal serial bus (USB) port,an audio jack, a power supply interface, one or more antennas, agraphics processor, an application processor, a speaker, a microphone,and other I/O components. The display may be an LCD or LED screenincluding a touch screen. The sensor may include a gyro sensor, anaccelerometer, a proximity sensor, an ambient light sensor, and apositioning unit. The positioning unit may communicate with componentsof a positioning network, e.g., a global positioning system (GPS)satellite.

The antennas 210 may comprise one or more directional or omnidirectionalantennas, including, for example, dipole antennas, monopole antennas,patch antennas, loop antennas, microstrip antennas or other types ofantennas suitable for transmission of RF signals. In some multiple-inputmultiple-output (MIMO) embodiments, the antennas 210 may be effectivelyseparated to take advantage of spatial diversity and the differentchannel characteristics that may result,

Although the communication device 200 is illustrated as having severalseparate functional elements, one or more of the functional elements maybe combined and may be implemented by combinations ofsoftware-configured elements, such as processing elements includingdigital signal processors (DSPs), and/or other hardware elements. Forexample, some elements may comprise one or more microprocessors, DSPs,field-programmable gate arrays (FPGAs), application specific integratedcircuits (ASICs), radio-frequency integrated circuits (RFICs) andcombinations of various hardware and logic circuitry for performing atleast the functions described herein. In some embodiments, thefunctional elements may refer to one or more processes operating on oneor more processing elements.

Embodiments may be implemented in one or a combination of hardware,firmware and software. Embodiments may also be implemented asinstructions stored on a computer-readable storage device, which may beread and executed by at least one processor to perform the operationsdescribed herein. A computer-readable storage device may include anynon-transitory mechanism for storing information in a form readable by amachine (e.g., a computer). For example, a computer-readable storagedevice may include read-only memory (ROM), random-access memory (RAM),magnetic disk storage media, optical storage media, flash-memorydevices, and other storage devices and media. Some embodiments mayinclude one or more processors and may be configured with instructionsstored on a computer-readable storage device.

FIG. 3 is a block diagram of a communication device in accordance withsome embodiments. The communication device 300 may be a STA 103 or AP102 shown in FIG. 1. In addition, the communication device 300 may alsobe suitable for use as an HE device 104 as shown in FIG. 1, such as anHE station. In some embodiments, the communication device 300 may besuitable for use as an EDMG device 105 as shown in FIG. 1, such as anEDMG station. Some of the components shown in FIG. 3 may not be presentin all of the devices in FIG. 1.

The communication device 300 may include physical layer circuitry 302for enabling transmission and reception of signals to and from themaster station 102, HE devices 104, EDMG devices 105, other STAs 103,APs and/or other devices using one or more antennas 201. The physicallayer circuitry 302 may perform various encoding and decoding functionsthat may include formation of baseband signals for transmission anddecoding of received signals. The communication device 300 may alsoinclude medium access control layer (MAC) circuitry 304 for controllingaccess to the wireless medium. The communication device 300 may alsoinclude processing circuitry 306, such as one or more single-core ormulti-core processors, and memory 308 arranged to perform the operationsdescribed herein. The physical layer circuitry 302, MAC circuitry 304and processing circuitry 306 may handle various radio control functionsthat enable communication with one or more radio networks compatiblewith one or more radio technologies. The radio control functions mayinclude signal modulation, encoding, decoding, radio frequency shifting,etc. For example, similar to the device shown in FIG. 2., in someembodiments, communication may be enabled with one or more of a WMAN, aWLAN, and a WPAN. In some embodiments, the communication device 300 canbe configured to operate in accordance with 3GPP standards or otherprotocols or standards, including WiMax, WiFi, GSM, EDGE, GERAN, UMTS,UTRAN, or other 3G, 3G, 4G, 5G, etc. technologies either alreadydeveloped or to be developed. The communication device 300 may includetransceiver circuitry 312 to enable communication with other externaldevices wirelessly and interfaces 314 to enable wired communication withother external devices. As another example, the transceiver circuitry312 may perform various transmission and reception functions such asconversion of signals between a baseband range and a Radio Frequency(RF) range.

The antennas 301 may comprise one or more directional or omnidirectionalantennas, including, for example, dipole antennas, monopole antennas,patch antennas, loop antennas, microstrip antennas or other types ofantennas suitable for transmission of RF signals. In some MIMOembodiments, the antennas 301 may be effectively separated to takeadvantage of spatial diversity and the different channel characteristicsthat may result.

Although the communication device 300 is illustrated as having severalseparate functional elements, one or more of the functional elements maybe combined and may be implemented by combinations ofsoftware-configured elements, such as processing elements includingDSPs, and/or other hardware elements. For example, some elements maycomprise one or more microprocessors, DSPs, FPGAs, ASICs, RFICs andcombinations of various hardware and logic circuitry for performing atleast the functions described herein. In some embodiments, thefunctional elements may refer to one or more processes operating on oneor more processing elements. Embodiments may be implemented in one or acombination of hardware, firmware and software. Embodiments may also beimplemented as instructions stored on a computer-readable storagedevice, which may be read and executed by at least one processor toperform the operations described herein.

In some embodiments, the communication device 300 may be configured asan HE device 104 (FIG. 1) and/or an EDMG device 105 (FIG. 1), and maycommunicate using OFDM communication signals over a multicarriercommunication channel. Accordingly, in some cases the communicationdevice 300 may be configured to receive signals in accordance withspecific communication standards, such as the Institute of Electricaland Electronics Engineers (IEEE) standards including IEEE 802.11-2012,802.11n-2009 and/or 802.11ac-2013 standards and/or proposedspecifications for WLANs including proposed HE standards and/or proposedEDMG standards, although the scope of the application is not limited inthis respect as they may also be suitable to transmit and/or receivecommunications in accordance with other techniques and standards. Insome other embodiments, the communication device 300 configured as an HEdevice 104 may be configured to receive signals that were transmittedusing one or more other modulation techniques such as spread spectrummodulation (e.g., direct sequence code division multiple access(DS-CDMA) and/or frequency hopping code division multiple access(FH-CDMA)), time-division multiplexing (TDM) modulation, and/forfrequency-division multiplexing (FDM) modulation, although the scope ofthe embodiments is not limited in this respect.

In accordance with embodiments, the STA 103 may transmit a grant frameto indicate a transmission of a data payload by the STA 103 during agrant period. The grant frame may indicate whether the data payload isto be transmitted on primary channel resources or on secondary channelresources. The STA 103 may transmit the data payload to a destinationSTA 103 on the secondary channel resources when the grant frameindicates that the data payload is to be transmitted on the secondarychannel resources. The grant frame may be transmitted on the primarychannel resources and on the secondary channel resources when the grantframe indicates that the data payload is to be transmitted on thesecondary channel resources. When the grant frame indicates that thedata payload is to be transmitted on the primary channel resources, thegrant frame may be transmitted on the primary channel resources and theSTA 103 may refrain from transmission of the grant frame on thesecondary channel resources. These embodiments will be described in moredetail below.

In some embodiments, the channel resources may be used for downlinktransmission by the AP 102 and for uplink transmissions by the STAs 103.That is, a time-division duplex (TDD) format may be used. In someembodiments, the channel resources may be used for direct communicationbetween one or more STAs 103. For instance, the STAs 103 may beconfigured to communicate in a peer-to-peer (P2P) mode. As anotherexample, the STAs 103 may be configured to communicate in a non PortControl Protocol/AP (non-PCP/AP) mode.

In some cases, the channel resources may include multiple channels, suchas the 20 MHz channels or 2.16 GHz channels previously described. Thechannels may include multiple sub-channels or may be divided intomultiple sub-channels for the uplink transmissions to accommodatemultiple access for multiple STAs 103. The downlink transmissions and/orthe direct transmissions between STAs 103 may or may not utilize thesame format.

In some embodiments, the sub-channels may comprise a predeterminedbandwidth. As a non-limiting example, the sub-channels may each span2.03125 MHz, the channel may span 20 MHz, and the channel may includeeight or nine sub-channels. Although reference may be made to asub-channel of 2.03125 MHz for illustrative purposes, embodiments arenot limited to this example value, and any suitable frequency span forthe sub-channels may be used. In sonic embodiments, the frequency spanfor the sub-channel may be based on a value included in an 802.11standard (such as 802.11ax and/or 802.11ay), a 3GPP standard or otherstandard.

In some embodiments, the sub-channels may comprise multiplesub-carriers. Although not limited as such, the sub-carriers may be usedfor transmission and/or reception of OFDM or OFDMA signals. As anexample, each sub-channel may include a group of contiguous sub-carriersspaced apart by a pre-determined sub-carrier spacing. As anotherexample, each sub-channel may include a group of non-contiguoussub-carriers. That is, the channel may be divided into a set ofcontiguous sub-carriers spaced apart by the pre-determined sub-carrierspacing, and each sub-channel may include a distributed or interleavedsubset of those sub-carriers. The sub-carrier spacing may take a valuesuch as 78.125 kHz, 312.5 kHz or 15 kHz, although these example valuesare not limiting. Other suitable values that may or may not be part ofan 802.11 or 3GPP standard or other standard may also be used in somecases. As an example, for a 78.125 kHz sub-carrier spacing, asub-channel may comprise 26 contiguous sub-carriers or a bandwidth of2.03125 MHz.

FIG. 4 illustrates another block diagram of a communication device inaccordance with some embodiments. In alternative embodiments, thecommunication device 400 may operate as a standalone device or may beconnected (e.g., networked) to other communication devices. In anetworked deployment, the communication device 400 may operate in thecapacity of a server communication device, a client communicationdevice, or both in server-client network environments. In an example,the communication device 400 may act as a peer communication device inpeer-to-peer (P2P) (or other distributed) network environment. Thecommunication device 400 may be a UE, eNB, AP, STA, PC, a tablet PC, aSTB, a PDA, a mobile telephone, a smart phone, a web appliance, anetwork router, switch or bridge, or any communication device capable ofexecuting instructions (sequential or otherwise) that specify actions tobe taken by that communication device. Further, while only a singlecommunication device is illustrated, the term “communication device”shall also be taken to include any collection of communication devicesthat individually or jointly execute a set (or multiple sets) ofinstructions to perform any one or more of the methodologies discussedherein, such as cloud computing, software as a service (SaaS), othercomputer cluster configurations.

Examples, as described herein, may include, or may operate on, logic ora number of components, modules, or mechanisms. Modules are tangibleentities (e.g., hardware) capable of performing specified operations andmay be configured or arranged in a certain manner. In an example,circuits may be arranged (e.g., internally or with respect to externalentities such as other circuits) in a specified manner as a module. Inan example, the whole or part of one or more computer systems (e.g., astandalone, client or server computer system) or one or more hardwareprocessors may be configured by firmware or software (e.g.,instructions, an application portion, or an application) as a modulethat operates to perform specified operations. In an example, thesoftware may reside on a communication device readable medium. In anexample, the software, when executed by the underlying hardware of themodule, causes the hardware to perform the specified operations.

Accordingly, the term “module” is understood to encompass a tangibleentity, be that an entity that is physically constructed, specificallyconfigured (e.g., hardwired), or temporarily (e.g., transitorily)configured (e.g., programmed) to operate in a specified manner or toperform part or all of any operation described herein. Consideringexamples in which modules are temporarily configured, each of themodules need not be instantiated at any one moment in time. For example,where the modules comprise a general-purpose hardware processorconfigured using software, the general-purpose hardware processor may beconfigured as respective different modules at different times. Softwaremay accordingly configure a hardware processor, for example, toconstitute a particular module at one instance of time and to constitutea different module at a different instance of time.

Communication device (e.g., computer system) 400 may include a hardwareprocessor 402 (e.g., a central processing unit (CPU), a graphicsprocessing unit (GPU), a hardware processor core, or any combinationthereof), a main memory 404 and a static memory 406, some or all ofwhich may communicate with each other via an interlink (e.g., bus) 408.The communication device 400 may further include a display unit 410, analphanumeric input device 412 (e.g., a keyboard), and a user interface(UI) navigation device 414 (e.g., a mouse). In an example, the displayunit 410, input device 412 and UI navigation device 414 may be a touchscreen display. The communication device 400 may additionally include astorage device (e.g., drive unit) 416, a signal generation device 418(e.g., a speaker), a network interface device 420, and one or moresensors 421, such as a global positioning system (GPS) sensor, compass,accelerometer, or other sensor. The communication device 400 may includean output controller 428, such as a serial (e.g., universal serial bus(USB), parallel, or other wired or wireless (e.g., infrared (IR), nearfield communication (NFC), etc. connection to communicate or control oneor more peripheral devices (e.g., a printer, card reader, etc.).

The storage device 416 may include a communication device readablemedium 422 on which is stored one or more sets of data, structures orinstructions 424 (e.g., software) embodying or utilized by any one ormore of the techniques or functions described herein. The instructions424 may also reside, completely or at least partially, within the mainmemory 404, within static memory 406, or within the hardware processor402 during execution thereof by the communication device 400. In anexample, one or any combination of the hardware processor 402, the mainmemory 404, the static memory 406, or the storage device 416 mayconstitute communication device readable media.

While the communication device readable medium 422 is illustrated as asingle medium, the term “communication device readable medium” mayinclude a single medium or multiple media (e.g., a centralized ordistributed database, and/or associated caches and servers) configuredto store the one or more instructions 424.

The term “communication device readable medium” may include any mediumthat is capable of storing, encoding, or carrying instructions forexecution by the communication device 400 and that cause thecommunication device 400 to perform any one or more of the techniques ofthe present disclosure, or that is capable of storing, encoding orcarrying data structures used by or associated with such instructions.Non-limiting communication device readable medium examples may includesolid-state memories, and optical and magnetic media. Specific examplesof communication device readable media may include: non-volatile memory,such as semiconductor memory devices (e.g., Electrically ProgrammableRead-Only Memory (EPROM), Electrically Erasable Programmable Read-OnlyMemory (EEPROM)) and flash memory devices; magnetic disks, such asinternal hard disks and removable disks; magneto-optical disks; RandomAccess Memory (RAM); and CD-ROM and DVD-ROM disks. In some examples,communication device readable media may include non-transitorycommunication device readable media. In some examples, communicationdevice readable media may include communication device readable mediathat is not a transitory propagating signal,

The instructions 424 may further be transmitted or received over acommunications network 426 using a transmission medium via the networkinterface device 420 utilizing any one of a number of transfer protocols(e.g., frame relay, internet protocol (IP), transmission controlprotocol (TCP), user datagram protocol (UDP), hypertext transferprotocol (HTTP), etc.). Example communication networks may include alocal area network (LAN), a wide area network (WAN), a packet datanetwork (e.g., the Internet), mobile telephone networks (e.g., cellularnetworks), Plain Old Telephone (POTS) networks, and wireless datanetworks (e.g., IEEE 802.11 family of standards, IEEE 802.16 family ofstandards), IEEE 802.15.4 family of standards, a LTE family ofstandards, a Universal Mobile Telecommunications System (UMTS) family ofstandards, peer-to-peer (P2P) networks, among others. In an example, thenetwork interface device 420 may include one or more physical jacks(e.g., Ethernet, coaxial, or phone jacks) or one or more antennas toconnect to the communications network 426 In an example, the networkinterface device 420 may include a plurality of antennas to wirelesslycommunicate using at least one of single-input multiple-output (SINK)),MIMO, or multiple-input single-output (MISO) techniques. In someexamples, the network interface device 420 may wirelessly communicateusing Multiple User MIMO techniques. The term “transmission medium”shall be taken to include any intangible medium that is capable ofstoring, encoding or carrying instructions for execution by thecommunication device 400, and includes digital or analog communicationssignals or other intangible medium to facilitate communication of suchsoftware.

As above, there are a number of positioning techniques in IEEE 802.11that may be used to determine the location of a STA. These techniquesinclude Angle of Arrival (AoA) and Angle of Departure (AoD), in whichdownlink transmissions from the AP may be measured at an antenna arrayof the STA or uplink transmissions of the STA may be measured at anantenna array of the AP. The AoD/AoA is the angle between thetransmission/reception direction of a reference signal from a linearantenna array and the normal axis of the array. In some cases, the TimeDifference of Arrival (TDOA) may be measured at individual elements ofthe array. The received AP signal between successive antenna elementsmay be phase-shifted, and the degree of phase shift may depend on theAoD/AoA, the antenna element spacing, and the carrier frequency. Bymeasuring the phase shift and using known AP characteristics, theAoD/AoA can be determined. In the embodiments described, the AP isreferred to as having transmitted the symbols, although in otherembodiments other wireless devices, such as another STA or otherwireless devices may transmit the symbols.

One issue with using AoA is that for user STAs, such as cell phones, theAoA may change dependent on the orientation of the STA, which mayconstantly move. Thus, AoD may be a more useful overall technique to usefor all types of STAs. Focusing in particular on AoD techniques, toimprove scalability for position determination, an AoD technique may beused in which the AP is the only device transmitting at a particularpoint in time, with the STAs only being listeners. This may remove thedependency of the number of location transmissions on the number ofSTAs. Typically when using the AoD technique, the AP may transmitpreambles from an antenna array while switching antennas to transmitdifferent packets. The receiving STA, e.g., a mobile device, may decodethese preambles and use the decoded information to estimate the AoD. TheSTA may thus perform a major part of the positioning calculation.Moreover, to perform the calculations, the STA may have previouslyobtained calibration data of the antennas from the AP and to store thisinformation in a memory of the STA. The calibration data may include therelationship between the angle and phase of every antenna elements inthe antenna array for each angle. This methodology may thus trade areduction in the amount of network traffic to perform the STApositioning with an increase of work being performed by the STA, as wellas an increased memory load with increasing numbers of antennas in theantenna array or increasing numbers of antenna arrays are used.

An AoD estimation method may be used in which one or more APs may beconfigured to transmit signals to one or more STAs in a plurality ofdiscrete directions and having a predefined order. The STA may then lookfor the signal with the strongest (and perhaps earliest) direction. TheAoD estimation method may be single sided, that is the AP(s) is the onlytransmitter and the STA acting only as a receiver (no transmissions).Thus, there may be a defined relationship between the direction andtiming of the transmissions, and in some circumstances, the signalcharacteristics. The AoD technique may use preambles to transmit one ormore symbols on different tones or may use data frames to transmit thesymbols on the different tones, and the different tones and/or symbolstransmitted on different angles.

The STA may be configured to detect one or more of the tones that have aparticular characteristic or combination of characteristics. Forexample, the STA may detect the strongest tone and/or a predeterminedtiming, such as the earliest tone. The latter may be useful when a largenumber of clusters or other scatterers are present, perhaps causing thestrongest tone to shift while the earliest arriving tone remains thetone being received via the most direct route (line of sight). Theearliest tone may be used in sonic embodiments to discriminate betweenmultiple tones When the tones have a signal strength within apredetermined range of each other and/or when a large number ofscatterers are present. The AP may use, in total, 117 tones having abandwidth of 40 MHz and a length of 4 ms. In other embodiments, for WiFithe number of tones may be variable with the bandwidth. For 40 MHz, forexample, there may be only 108 available subcarriers in the datasymbols. Several tones (as predefined by the standard as pilot tones)can still be used for phase and amplitude tracking. This may be done foreach data symbol to help against certain impairments of the STAs; suchpilots can thus be expected to still be used in the AoD symbols.Moreover, the length of the symbol may be variable—in 802.11a/b/g/n/acit can be 3.6 μs to 4 μs. For 802.11ax (which is currently beingdeveloped), the symbol duration can range from 3.2 μs to 16 μs.

The AP may transmit OFDM symbols in the plurality of directions. Inparticular, the AP may be configured to simultaneously transmit eachOFDM symbol (or set of OFDM symbols) using a different tone, or morethan one OFDM symbol or tone, in a different direction according to apattern known to the STA. Each tone transmitted in a particulardirection may be unique, that is, different from each other tonetransmitted in each other direction. An AoD estimation method may beused in which one or more APs may be configured to transmit signals toone or more STAs in a plurality of discrete directions and having apredefined order.

Simultaneous transmission using all of the AP antennas, while allowingsimple estimation of AoD by the receiver, may be costly and complex. Inother embodiments, only a few or even a single transmit chain may beused for multiple antenna, allowing the signals to be transmitted atdifferent times by switching the AP transmit chains between allavailable antennas. Thus, instead of transmitting a single symbolsimultaneously using each antenna, each symbol may be transmitted usingdifferent sets of antennas at different times. The STA may receive andbuffer the symbols. The STA may then sum the buffered symbols into asingle symbol, thus emulating an AP with a large number of transmitchains. The reception of the buffered symbols may occur over arelatively short time period, and thus the channel between the STA andAP may be linear and time-invariant. The result of the summation of thesymbols into a single symbol by the STA may thus be equivalent to theresult of transmitting a single symbol simultaneously from all the AP'santennas. One or more buffers whose total memory is the size of an OFDMsignal may be sufficient to sum a new symbol, continuing until allsymbols are received from the AP.

While the channel may remain substantially constant, however, switchingof the antennas during the packet can take several μs. During this time,the switching process may introduce artificialities into the transmittedsignal. To this end, the AP may indicate to the STA to ignore apredetermined number of symbols between each of the times in which theAP transmits through different antennas. During these times, the AP maybe expected to be transmitting non-valid signals or even stopping thetransmission entirely, until it finishes its switching process. In someembodiments, the AP may transmit an announcement frame beforetransmitting the packet which is used for the AoD estimation. Theannouncement frame may contain a variety of information for use by theSTA, including the number of symbols transmitted between each switchingoperation, the number of symbols used for the switching operation, thecodebook that maps the tones in each symbol to their respective physicalangles if not set by the standard, and optionally data regardingcalibration and/or beamshape patterns that can be used by the STA forthe estimation process. In other embodiments, some or all of thisinformation may be contained within header fields of the header.

Either method (simultaneous or sequential transmission) may assume thatall AP antennas are calibrated and no phase shift errors exist duringthe time it takes for the switching to complete so that the switchingprocess does not affect the actual data transmitted after switching. Ina real system, however, after each switching process, a global unknownphase may be added to all transmit chains due to a phase shift in time.Phase shift errors in general can be caused by a few factors, such asfrequency offset between the AP (transmitter) and STA (receiver).Moreover, the switching from one set of antennas to the next can causeextra phase and amplitude errors. While pilot tones may be used by theSTA to track these changes, no valid data can be transmitted during theswitching process. Thus, standard phase and amplitude tracking may beunable to be employed.

In addition, some systems are unable to perform switching during anactive transmission. Instead, several packets may be transmitted by theAP, each from a different set of antennas. The amplitude and phase canchange drastically between the packets, which may introduce even greateramplitude and phase changes to be corrected.

Moreover, sufficiently accurate calibration of large antenna arrays maynot be possible. Unfortunately, all antennas are expected to becalibrated such that their phases and amplitude gains are known. As thesize of the antenna array grows, this process may become increasinglydifficult since the calibration is to be performed simultaneously on allof the antennas.

In some receivers such as STAs, buffering and processing of all of thepreamble symbols may not be possible without resorting to using multiplepackets. Notably, the current 802.11ac standard supports non-datapackets with up to 8 preambles, so many systems have been designed toonly handle 8 preambles at a time. This may introduce further phase andamplitude distortions.

Thus, calibration difficulties and phase shift (drift) errors may existin the above AoD determination methods. To handle these errors, a phaseand amplitude sync method and/or a relative phase method may beperformed. The phase and amplitude sync method may synchronize the phaseand amplitude of the transmitted signal after each switching process. Inone embodiment, the transmitter may transmit the same symbol from apredefined antenna before and after each switching process. The receivermay use this symbol to track the phase and amplitude differences due tothe switching process. In the relative phase method, on the other hand,syncing may be avoided. Instead, the receiver may use the relativephases between received symbols to eliminate (or be invariant to)unknown phase changes caused by the switching process. In one example,the relative phase of pairs of received symbols may be used. One or bothmethods also support switching during an active transmission, as well asswitching antennas in between packets. The transmit chains of thetransmitter may be calibrated to have a known phase and amplitude inrelation to the other. Moreover, phase shift (drift) errors caused bythe time to perform the switching process may be reduced.

FIG. 5 illustrates a transmission from an AP at an AoD in accordancewith some embodiments. The AP 502 and. STA 508 may be any of the devicesshown in FIGS. 1-4. The AP 502 may have multiple antenna elements, forexample, arranged in an antenna array. The AP 502 may transmit OFDMsymbols at an AoD of θ to the STA 508. The AoD may depend on the numberof transmissions by the AP 502 or the number of antennas in the AP 502,with the AoD decreasing with increasing number. The STA 508 may havemultiple antennas and different transmit chains associated with eachantenna.

Once the symbols are detected, the STA 508 may subsequently estimate theAoD of the direct (line-of-sight) signal. Once the AoD is estimated bythe STA 508, a positioning solution can be achieved for the STA 508. Theuse of a single AP 502 whose location is known, for example, may serveto enable the STA 508 location to be determined in two dimensions,assuming the relative height difference between the AP 502 and the STA508 height is known. In other embodiments, multiple APs may be used todetermine the STA 508 position in three dimensions using triangulation.

As shown in FIG. 5, the AP 502 may have N_(tx) antennas 506 andN_(chains) transmit chains 504 for example. The number of antennas 506may in some embodiments be equal to or greater than the number oftransmit chains 504. In some embodiments, the AP 502 may transmit asingle symbol from each antenna 506. For example, the AP 502 maytransmit the first symbol using the first antenna (antenna 1) 506. Thenext N_(chains)−1 symbols may be transmitted using the same number ofantennas 506 (antenna 2 to antenna N_(chains)), using a differentantenna 506 to transmit a different symbol. The AP 502 may subsequentlyswitch the transmit chains 504 to use the next set of antennas 506 fortransmission of the symbols. This set may be antennas 506 numberedN_(chains)+1 to 2N_(chains). This may continue until a maximum of N_(tx)symbols are transmitted. In some embodiments, the AoD determination maybe performed after N_(tx) symbols are transmitted while in otherembodiments, multiple sets of N_(tx) symbols may be used in the AoDdetermination. When multiple sets of symbols are used, the symbols fromeach antenna may be aggregated individually and the resulting aggregatedsymbol from each antenna compared with the aggregated symbols from eachother antenna in the AoD determination.

FIG. 6 is a calibration method transmission from an AP in accordancewith some embodiments. The transmission 600 may be a packet and may beperformed by any of the APs shown in FIGS. 1-5. The packet 600 comprisesone or more headers as well as a payload comprising a plurality ofsymbols. The header may comprise a legacy and/or HE header. The headermay also be used to replace or supplement the symbol information in anannouncement frame, as indicated above. The packet 600 may be a packetthat may contain, for example, 8 or more symbol locations. As shown,data (a symbol) may be transmitted in some of the symbol locations, andin other symbol locations symbols may not be transmitted, as indicatedabove. Depending on the symbol location, the symbol may be transmittedby one or more antennas and use different sets of antennas by switchingthe transmit chains.

In particular, the transmit chains may be switched to the antennasnumbered [1, N_(chains)+1:2N_(chains)−1]. Thus, the first antenna may beused for each symbol that is transmitted, with the initial symbolimmediately after the header being transmitted by the first antenna. Thefirst symbol may be transmitted by the first antenna, but not by anyother antenna. The symbol transmitted by the first antenna may also bereferred to as the correction symbol while the symbol transmitted by theother antennas may be referred to as the AoD symbol. Note that the firstantenna is used as an example, in other embodiments, any antenna may beused to transmit the correction symbol. In some embodiments, only asingle antenna (e.g., the first antenna as indicated in FIG. 6) maytransmit the correction symbol; no other transmitter may transmit thecorrection symbol. In other embodiments, to ensure that the transmitpower remains the same, the antennas used to transmit the AoD symbolafter a particular correction symbol may transmit the carrier wave ofthe tone without the modulation of the correction symbol. Each thecorrection symbol (transmitted before and after the switching) may bethe same. As above, the channel may also remain the same throughouttransmission of the packet 600. Since the signal (the correction symbol)and the channel from the first antenna before and after the switchingare the same, the STA may be estimate the change in phase and amplitudecaused by the switching operation using the correction symbol. Thischange may be applied to the AoD symbols transmitted by the remainingantennas to normalize the information for AoD calculation by the STA.

As shown, symbols may be transmitted in pairs, a correction symbol andan AoD symbol. The number of pairs in the packet 600 may depend on thenumber of transmit chains, the number of antennas and the availablebuffer memory. As shown in FIG. 6, the first symbol transmitted in eachcluster may be transmitted using only the first antenna and the nextsymbol transmitted using the first antenna and other antennas to whichthe transmit chains have been switched. As above, the same correctionsymbol may be transmitted in each pair. The AoD symbol may beindependent of the correction symbol (the symbols may or may not be thesame). In some embodiments, the symbol location of the correction symbolmay be the second location or may vary, as indicated by the announcementframe and/or header. In some embodiments, it may be sufficient totransmit the same correction symbol and for the STA to be able todiscriminate between the symbol correction location and the AoD symbollocation.

In some embodiments, the symbols received before the switching may beindicated as:[h₁e^(ϕ) ¹ A₁, h₂e^(ϕ) ¹ A₁ . . . h_(N) _(chains) e^(ϕ) ¹ A₁],

where h_(j) is the channel from transmit antenna j, and e^(ϕ) ¹ , A₁ arerandom phase and amplitude added to all antennas. The symbols after theswitching operations can then be indicated as:[h₁e^(ϕ) ² A₂, h_(N) _(chains) ₊₁e^(ϕ) ² A₂ . . . h_(2N) _(chains−1)e^(ϕ) ² A₂],

where the same notation is used, only now a different global amplitudeand phase are present. The STA can estimate the factor e^(ϕ) ² A₂/e^(ϕ)¹ A₁ using the correction symbols transmitted from the first antenna inthe first and second pairs of FIG. 6. The STA may then use the factor tocorrect the phase and amplitude of the AoD symbols after the switchingfrom the remaining antennas. This correction can be calculatedimmediately once the correction symbol is received after the switching.Once the STA can correct the phases and amplitudes, and has received theAoD symbol, the STA can estimate the AoD of the symbols. As the symbolsbetween the correction-AoD symbol pairs may be unused due to theswitching, this may provide sufficient time to perform the correctiondetermination and correction on the AoD symbols, although the firstsymbol after the switching may be used for the correction symbol toprovide the maximum time for the correction calculation.

The phase and amplitude estimation and correction operations may berepeated after each switching of the packet. In some embodiments, thecorrection factor may be assumed to be the same after every switching inthe packet. Thus, only a single pair of correction symbol may be used.In this case, the pair of correction symbols may be disposed in adjacentpairs or at any point within the packet, so long as the STA is providedthe information of the correction symbol locations and the number ofswitchings between the correction symbols. Likewise, the correction tothe AoD symbols may be performed on all but one of the AoD symbols. Thismay reduce the number of symbols used in the packet. In otherembodiments, the correction factor may not be assumed to remain constantafter every switching in the packet. Thus, the correction symbol may betransmitted in every correction-AoD symbol pair. While any twocorrection symbols may be used to determine the correction to thecorresponding AoD symbol (and correct to a particular AoD symbol),although using the correction symbol pairs of the initial correctionsymbol after the header and the correction symbol of a particularcorrection-AoD symbol pair may be relatively simple.

In FIG. 6, a single packet is used for the AoD determination. However,in some embodiments, multiple frames may be used. FIG. 7 is anothercalibration method transmission from an AP in accordance with someembodiments. As shown, the switching may be performed in the timebetween transmission of the two packets 700. Multiple packets may beused to reduce the buffer size used in determining the AoD. Similar tothe above, the number of packets and number of symbols in the packets inFIG. 7 may depend on the number of transmit chains, the number ofantennas and the buffer size—e.g., the larger the buffer, the larger thenumber of symbols able to be used in a packet and the fewer number ofpackets for correction and AoD determination.

By buffering the symbols used for the syncing the STA may be able togain performance in low SNR situations. Without buffering, thecalibration method may estimate only the phase and amplitude in thesymbols used for the AoD estimation—relative to the syncing symbol forthat transmission section. This may be used since the syncing symbol isthe same in each transmission section, up to the unknown global phaseand amplitude caused by the switching, and maybe some pre-knowndeterministic factor that the AP already signaled in the announcementframe.

As shown in FIGS. 6 and 7, to reduce the number of transmit chains usedto estimate the phase and amplitude changes due to the switching, only asingle antenna may be used to transmit the same symbol at the start ofeach transmission section, following the switching. In addition, fewerthan all of the OFDM tones may be used for the estimation of the changein amplitude and phase.

In particular, in some embodiments, estimation of the change in phaseand amplitude caused by the switching operation may be performed using aplurality of OFDM tones, such as all of the available tones. In someembodiments, a limited set of OFDM tones may be used by each of multipleantennas to transmit the correction symbol in the correction symbollocation. For example, two antennas may be used to transmit thecorrection symbol in the correction symbol location; one antennatransmitting on every even OFDM tone of the available OFDM tones and theother antenna transmitting on every odd OFDM tone of the available OFDMtones. Other sets of OFDM tones, rather than even and odd, may be usedfor transmission—such as higher and lower ranges of OFDM tones or setsof OFDM tone ranges. The OFDM tones may be divided equally among theantennas or may be unequal as desired. This may permit the correctionsymbols from multiple antennas to be compared for correction purposes.Note that the relationship between the AoD and the tones may provided bythe codebook in the announcement frame or in another frame, so that onlycertain tones may be used by particular antennas when transmitting atparticular AoDs.

In some embodiments, independent of the number of antennas used totransmit the correction symbol fewer than all of the OFDM tones may beused—for example if severe noise exists on the unused OFDM tones, toincrease the signal to noise (SNR) or SINK ratio for the correctionsymbol. This information may be provided to the STA in the announcementframe or in the header, for example. The use of fewer tones for acorrection symbol, however, may degrade the estimation performance.

Thus, the calibration method described may avoid calibration of theentire array at once. Instead, it may be sufficient to obtain theamplitude and phase of the transmission for each antenna for each of theswitching configurations relative to each other. Rather than use thecalibration method, in other embodiments, a relative phase method may beused. FIG. 8 is a relative phase method transmission from an AP inaccordance with some embodiments.

The relative phase method may assume that the amplitude remainssubstantially constant over at least the packet 800, if not the AoDestimation period. In the relative phase method, the relative phase isdetermined between pairs of symbols that belong to the same transmissionsection. As shown in FIG. 8, the packet 800 may include a header,followed by several symbols, each of which may be transmitted bydifferent antennas. The STA can multiply the first and second symbolsand add to this total to the multiplication of fifth and sixth symbols.In some embodiments, the first symbol can have an unknown phase if thestandard does not force the AP to transmit the headers in specificfashion, such as only using the first antenna. The phase on the firstsymbol may thus be cancelled before being combined with the remaining.In some embodiments, the headers may be limited to being transmitted ina predetermined manner, for example using only a single antenna whilethe rest of the antennas connected to the transmit chains transmit onlya carrier wave. Although in FIG. 8 a specific antenna is referred to astransmitting the first symbol, other antennas may transmit the samesymbol, so long as the number of antennas transmitting the symbolremains limited by the number of transmit chains. The switching mayoccur after transmission of the last symbol transmitted by the antennaattached to the last of the transmit chains. Similar to FIGS. 6 and 7,transmission may not occur for two or more symbols, depending on theamount of time it takes for the transmitter chains to switch to the newantennas. In the example shown in FIG. 8, a pair of symbols istransmitted before the switching; the number of transmit chains is two.After switching, another pair of symbols may be transmitted.

In other embodiments, the initial symbol after the header may betransmitted by multiple antennas and the initial symbol after theswitching may be transmitted by one of the antennas that transmitted thefirst symbol. The initial symbol after the header may be used AoD andthe terminal symbol may be used both for AoD and for phase correction.The terminal symbol may be transmitted by a pair of antennas, both ofwhich may be different than the antennas that transmitted the firstsymbol. The signal provided by one of the antennas of the pair ofantennas may be multiplied by the complex conjugate of the other of theantennas of the pair of antennas. This multiplication may cancel aglobal unknown phase caused by the switching process. The remainingsymbols from the antennas of the pair of antennas may then be used alongwith the first symbol to determine the AoD. The AP may indicate to theSTA, either in the announcement frame or the header, which symbols tomultiply together and add together. The symbols may be predetermined bythe AP to permit the STA to accurately determine the AoD. The relativephase method can reduce the number of symbols for the AoD determinationcompared with the calibration method, but at the cost of addedcomplexity and reduced performance due to the pre-computation at the APand the complex multiplication and addition at the STA.

FIG. 9 illustrates a method of determining AoD in accordance with someembodiments. The method may be performed by any of the STAs shown anddescribed in FIGS. 1-5. Embodiments of the method may thus includeadditional or fewer operations or processes in comparison to what isillustrated in FIG. 9. In addition, embodiments of the method are notnecessarily limited to the chronological order that is shown in FIG. 9.The method may be practiced with suitable systems, interfaces andcomponents. In addition, while the method and other methods describedherein may refer to STAs operating in accordance with IEEE 802.11 orother standards, embodiments of those methods are not limited to justthose STAs and may also be practiced by other mobile devices.

At operation 902, the STA may initialize a channel buffer. The channelbuffer may have a predetermined size, such as that of the OFDM symbol.The initialization may set the buffer to 0.

The STA may at operation 904 start receiving the packet. The packet maybe provided over some or all of the available OFDM tones. The packet maycontain a legacy or HE header frame.

The packet at operation 906 may be preceded by an announcement framethat has been received by the STA. The announcement frame may describethe packet. The announcement frame may include the number of symbolstransmitted between each switching operation, the number of symbols usedfor the switching operation, the codebook that maps the tones in eachsymbol to their respective physical angles if not set by the standard,and optionally data regarding calibration and/or beamshape patterns thatcan be used by the STA for the estimation process. The announcementframe may also indicate to the STA that this information may becontained within header fields of the header.

At operation 908 the STA may determine whether to use a particularpreamble (i.e., symbol) for AoD determination. The determination forpreamble number i may be indicated in one or both the announcement frameor header.

If the STA determines at operation 908 that a particular preamble is notto be used for the AoD determination, the STA may at operation 910 waitfor the next preamble. The STA may increment the preamble number i by 1and return to operation 908 for the next preamble. The STA may ignorethe preamble as this signal may be the signal during the transitionperiod between the pair of symbols.

In response to a determination at operation 908 that a particularpreamble is to be used for the AoD determination, the STA may atoperation 912 estimate the channel for preamble number i. The STA maythus estimate the symbol at this point in time.

The announcement frame may provide additional information than whether aparticular frame is not to be used. As indicated, at operation 914 theannouncement frame may indicate the specific purpose or position of eachsymbol.

The STA may use the information in the announcement frame to determinethe position of preamble number i. In particular, at operation 916 theSTA may determine whether preamble number i is the first symbol afterswitching has occurred. In other embodiments, a symbol other than thefirst after switching may be used.

If at operation 916 the STA determines that preamble number i is thefirst symbol after switching has occurred, the STA may at operation 918use the symbol in a correction estimation. The STA may specifically usethe symbol to determine the phase and perhaps amplitude change due tothe latest switching.

As shown in operation 920, the STA may have additional information toobtain the phase and amplitude change. In particular, the STA may usethe channel estimation of a symbol previously transmitted by the sameantenna prior to the switching. The channel estimation may be that ofthe transmission immediately preceding the switching or a predeterminednumber of times prior to the switching.

At operation 922 the STA may correct the phase and/or amplitude of thecurrent preamble. The correction may be based on the change(s)determined in operation 920. In some circumstances, no correction may beperformed.

At operation 924, after correction the STA may determine whetheradditional preambles exist. This is to say that additional antennas areto be tested due to the limited number of transmit chains. If additionalantennas are to be tested, the STA may return to operation 910.

At operation 926, the STA determines that preamble number i is not thefirst symbol after switching has occurred. The STA may then use thecorrection determined at operation 918 to correct for the phase and/oramplitude of the symbol just received.

At operation 928, the correction determined at operation 918 may besupplied to the STA for the correction at operation 926. As indicated,the latest correction determined at operation 918 (determined at thelast switching) may be used at operation 926.

At operation 930, the estimated preamble, which has been corrected, maybe added to the buffer. The additional information may be added based onlimitations of the buffer. If the buffer is full, additional packets maybe used for the ADD determination. After operation 930, the method maycontinue to operation 924.

If at operation 924 the STA determines that the last preamble to be usedhas been corrected for, the STA may at operation 932 determine the AoD.The STA may use the information stored in the buffer to determine theAoD of the symbols and determine the STA location.

To determine the AoD at operation 932, the STA may use information aboutthe angle and tone used. The relationship between the angle and tone maybe provided by the announcement packet or by the header.

EXAMPLES

Example 1 is an apparatus of a station (STA), the apparatus comprising:a memory; and processing circuitry arranged to: decode a first andsecond symbol from another wireless device, the first symbol receivedfrom a same antenna of the other wireless device; decode a third symbolfrom a first plurality of antennas of the other wireless device;determine a phase correction based a comparison between the first andsecond; correct a phase of a fourth symbol from a second plurality ofantennas of the other wireless device using the phase correction toproduce a corrected symbol, the first and second plurality of antennasbeing different; and estimate an Angle of Departure (AoD) of the othersymbol based on the corrected symbol.

In Example 2, the subject matter of Example 1 optionally includes thatthe processing circuitry is arranged to: correct the phase and anamplitude of the fourth symbol using the comparison.

In Example 3, the subject matter of Example 2 optionally includes thatthe first and second symbols are disposed in a packet, the packetcomprises a header and a plurality of symbols thereafter, the pluralityof symbols comprising pairs of symbols separated by a switching periodduring which signals received from the other wireless device areignored.

In Example 4, the subject matter of Example 3 optionally includes thateach pair of symbols comprises a correction symbol and an AoD symbol,the correction symbol disposed before the AoD symbol, the first andsecond symbols being the correction symbols and the third and fourthsymbols being the AoD symbols.

In Example 5, the subject matter of Example 4 optionally includes thatthe correction symbols are received from a single antenna and free frombeing received by other antennas of the other wireless device, and eachAoD symbol is received from a plurality of antennas.

In Example 6, the subject matter of Example 5 optionally includes thatthe processing circuitry is arranged to: correct the phase and amplitudeof the AoD symbol of a particular pair using a comparison between acorrection symbol immediately after the header and a correction symbolof the particular pair.

In Example 7, the subject matter of any one or more of Examples 3-6optionally include that a number of pairs of symbols in the packet isdependent on a number of transmit chains, a number of antennas and anamount of buffer memory in the memory, the buffer memory arranged tostore the correction symbols.

In Example 8, the subject matter of any one or more of Examples 3-7optionally include that the first and second symbols are disposed indifferent packets, each packet comprises a header and a pair of symbolscomprising a correction symbol and an AoD symbol, the correction symboldisposed before the AoD symbol, the first and second symbols being thecorrection symbols and the third and fourth symbols being the AoDsymbols.

In Example 9, the subject matter of any one or more of Examples 1-8optionally include that the processing circuitry is further arranged to:determine the phase correction using the comparison, the first andsecond symbol received from a first antenna on a first set of tones andthe first and second symbol received from a second antenna on a secondset of tones different from the first set of tones.

In Example 10, the subject matter of any one or more of Examples 1-9optionally include that the processing circuitry is further arranged to:decode at least one packet prior to reception of the first and secondsymbols, the at least one packet comprising a header, and decode packetinformation comprising a number of symbols in each set of symbols, anumber of symbols between adjacent sets, and a codebook that maps tonesin each symbol to respective physical angles, the packet informationcontained in at least one of: the header, and an announcement framereceived prior to the at least one packet.

In Example 11, the subject matter of any one or more of Examples 1-10optionally include that the processing circuitry is further arranged to:decode a same symbol from different antennas transmitted on differenttones in which an AoD for each tone is unique, determine whether phasecorrection is to be performed on the same symbol of the different tonesand correct phases of the same symbol of the different tones in responseto a determination that phase correction is to be performed, andestimate the AoD for the different tones through use of a codebookreceived in an announcement frame prior to a packet containing the firstand second symbols, the codebook relating the different tones to theAoD.

In Example 12, the subject matter of any one or more of Examples 1-11optionally include, further comprising: one or more antennas arranged toreceive the symbols from the other wireless device.

Example 13 is an apparatus of a wireless device, the apparatuscomprising: a transceiver; and processing circuitry arranged to: causethe transceiver to transmit, to a station (STA) through use of a firstantenna, a header and a first symbol; switch transmitter chains betweena first set of antennas and a second set of antennas after transmissionof the first symbol, a number of transmitter chains being smaller than anumber of antennas; after the switch, cause the transceiver to transmit,to the STA through use of the first antenna, another first symbol; andcause the transceiver to receive location information from the STA, thelocation information based on an angle of departure (AoD) estimatedependent on use of the first symbol and the other first symbol tocorrect for a phase and amplitude variation caused by the switch.

In Example 14, the subject matter of Example 13 optionally includes thatthe processing circuitry is further arranged to: avoid transmissionduring the switch.

In Example 15, the subject matter of any one or more of Examples 13-14optionally include that the processing circuitry is further arranged to:during the switch, cause the transmitter to transmit a carrier wave andavoid transmission of a symbol.

In Example 16, the subject matter of any one or more of Examples 13-15optionally include that the processing circuitry is further arranged to:cause the transmitter to transmit a second symbol after both the firstsymbol and the other first symbol, the second symbol transmitted afterthe first symbol transmitted by the first set of antennas and the secondsymbol transmitted after the second symbol transmitted by the second setof antennas, the first and second set of antennas comprising the firstantenna.

In Example 17, the subject matter of Example 16 optionally includes thatthe processing circuitry is further arranged to: cause the transmitterto transmit a packet comprising the header, a first pair of symbolscomprising the first symbol and one of the second symbols immediatelyafter the first symbol, and a second pair of symbols comprising theother first symbol and another of the second symbols immediately afterthe other first symbol, the first and second pair of symbols separatedby a switching period during which the transmitter chains are switchedbetween the first and second sets of antennas.

In Example 18, the subject matter of any one or more of Examples 16-17optionally include that the processing circuitry is further arranged to:cause the transmitter to transmit: a first packet comprising the headerand a first pair of symbols comprising the first symbol and one of thesecond symbols immediately after the first symbol, and a second packetcomprising the header and a second pair of symbols comprising the otherfirst symbol and another of the second symbols immediately after theother first symbol.

In Example 19, the subject matter of any one or more of Examples 13-18optionally include that transmission of the first symbol and the otherfirst symbol is limited to the first antenna.

In Example 20, the subject matter of any one or more of Examples 13-19optionally include that the processing circuitry is further arranged to:cause the transmitter to transmit: the first symbol from the firstantenna on a first set of tones and the other first symbol from thefirst antenna on the first set of tones, and the other first symbol froma second antenna on a second set of tones and the other first symbolfrom the second antenna on the second set of tones.

In Example 21, the subject matter of any one or more of Examples 13-20optionally include that the processing circuitry is further arranged to:transmit, prior to transmission of the header and first symbol, anannouncement frame, the announcement frame comprising packet informationcomprising a number of symbols between adjacent switches of thetransceiver chain, a number of symbols over which a particular switchoccurs, and a codebook that maps tones in each symbol to respectivephysical angles.

In Example 22, the subject matter of any one or more of Examples 13-21optionally include that wherein the wireless device is an access point(AP).

Example 23 is a computer-readable storage medium that storesinstructions for execution by one or more processors of a station (STA),the one or more processors to configure the STA to: decode a pair ofcomparison symbols from a first antenna of an access point (AP); decodea first and second Angle of Departure (AoD) symbol respectively from afirst and second set of antennas, wherein the first and second set ofantennas comprise different antennas that comprise the first antenna;determine a phase and amplitude correction based on a phase andamplitude change between the first and second comparison symbols; andcorrect a phase and amplitude of a second AoD symbol from the second setof antennas through use of the phase and amplitude correction to producea corrected AoD symbol for the second set of antennas.

In Example 24, the subject matter of Example 23 optionally includes thatthe comparison and. AoD symbols are disposed in a packet that comprisesa header, the packet comprising the first comparison symbol and firstAoD symbol separated from the second comparison symbol and second AoDsymbol by a period during which signals from the AP are ignored.

In Example 25, the subject matter of any one or more of Examples 23-24optionally include that the first comparison symbol and first AoD symbolare disposed in a first packet that comprises a first header, and thesecond comparison symbol and second AoD symbol are disposed in a secondpacket that comprises a second header.

In Example 26, the subject matter of any one or more of Examples 23-25optionally include that the one or more processors further configure theSTA to: decode an announcement frame prior to reception of the firstcomparison symbol, the announcement frame comprising packet informationcomprising a number of symbols in each set of symbols comprising acomparison symbol and an AoD symbol, a number of symbols betweenadjacent sets, and a codebook that maps tones in each symbol torespective physical angles.

Example 27 is a method of estimating an Angle of Departure (AoD) ofsymbols from a station (STA), the method comprising: decoding a pair ofcomparison symbols from a first antenna of an access point (AP), a firstcomparison symbol of the comparison symbols received prior to switchingof transmitter chains from a first set of antennas to a second set ofantennas and a second comparison symbol of the comparison symbolsreceived after the switching, the first and second set of antennascomprising the first antenna; decoding a first AoD symbol from the firstset of antennas; determining a phase and amplitude correction based on aphase and amplitude change between the first and second comparisonsymbols; correcting a phase and amplitude of a second AoD symbol fromthe second set of antennas through use of the phase and amplitudecorrection to produce a corrected AoD symbol for the second set ofantennas; and estimating an AoD of the first and second AoD symbolsbased on the first AoD symbols from the first set of antennas and thecorrected AoD symbol from the second set of antennas.

In Example 28, the subject matter of Example 27 optionally includes thatone of: the comparison and AoD symbols are disposed in a packet thatcomprises a header, the packet comprising the first comparison symboland first AoD symbol separated from the second comparison symbol andsecond AoD symbol by a switching period during which the transmitterchains are switched between the first and second sets of antennas, andthe method further comprises ignoring received signals during theswitching period, or the first comparison symbol and first AoD symbolare disposed in a first packet that comprises a first header, and thesecond comparison symbol and second AoD symbol are disposed in a secondpacket that comprises a second header.

Example 29 is an apparatus of a station (STA), the apparatus comprising:means for decoding a pair of comparison symbols from a first antenna ofan access point (AP), a first comparison symbol of the comparisonsymbols received prior to switching of transmitter chains from a firstset of antennas to a second set of antennas and a second comparisonsymbol of the comparison symbols received after the switching, the firstand second set of antennas comprising the first antenna; means fordecoding a first Angle of Departure (AoD) symbol from the first set ofantennas; means for determining a phase and amplitude correction basedon a phase and amplitude change between the first and second comparisonsymbols; means for correcting a phase and amplitude of a second AoDsymbol from the second set of antennas through use of the phase andamplitude correction to produce a corrected AoD symbol for the secondset of antennas; and means for estimating an AOD of the first and secondAoD symbols based on the first AoD symbols from the first set ofantennas and the corrected AoD symbol from the second set of antennas.

In Example 30, the subject matter of Example 29 optionally includes thatone of: the comparison and AoD symbols are disposed in a packet thatcomprises a header, the packet comprising the first comparison symboland first AoD symbol separated from the second comparison symbol andsecond AoD symbol by a switching period during which the transmitterchains are switched between the first and second sets of antennas, andthe method further comprises ignoring received signals during theswitching period, or the first comparison symbol and first AoD symbolare disposed in a first packet that comprises a first header, and thesecond comparison symbol and second AoD symbol are disposed in a secondpacket that comprises a second header.

Although an embodiment has been described with reference to specificexample embodiments, it will be evident that various modifications andchanges may be made to these embodiments without departing from thebroader scope of the present disclosure. Accordingly, the specificationand drawings are to be regarded in an illustrative rather than arestrictive sense. The accompanying drawings that form a part hereofshow, by way of illustration, and not of limitation, specificembodiments in which the subject matter may be practiced. Theembodiments illustrated are described in sufficient detail to enablethose skilled in the art to practice the teachings disclosed herein.Other embodiments may be utilized and derived therefrom, such thatstructural and logical substitutions and changes may be made withoutdeparting from the scope of this disclosure. This Detailed Description,therefore, is not to be taken in a limiting sense, and the scope ofvarious embodiments is defined only by the appended claims, along withthe full range of equivalents to which such claims are entitled.

Such embodiments of the subject matter may be referred to herein,individually and/or collectively, by the term “embodiment” merely forconvenience and without intending to voluntarily limit the scope of thisapplication to any single inventive concept if more than one is in factdisclosed. Thus, although specific embodiments have been illustrated anddescribed herein, it should be appreciated that any arrangementcalculated to achieve the same purpose may be substituted for thespecific embodiments shown. This disclosure is intended to cover any andall adaptations or variations of various embodiments. Combinations ofthe above embodiments, and other embodiments not specifically describedherein, will be apparent to those of skill in the art upon reviewing theabove description.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, UE,article, composition, formulation, or process that includes elements inaddition to those listed after such a term in a claim are still deemedto fall within the scope of that claim. Moreover, in the followingclaims, the terms “first,” “second,” and “third,” etc. are used merelyas labels, and are not intended to impose numerical requirements ontheir objects.

The Abstract of the Disclosure is provided to comply with 37 C.F.R.§1.72(b), requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the claims. In addition, in the foregoing DetailedDescription, it can be seen that various features are grouped togetherin a single embodiment for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as reflecting anintention that the claimed embodiments require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus the following claims are herebyincorporated into the Detailed. Description, with each claim standing onits own as a separate embodiment.

What is claimed is:
 1. An apparatus of a station (STA), the apparatuscomprising: a memory; and processing circuitry arranged to: decode afirst and second symbol from a first antenna of another wireless device;decode a third symbol from a first plurality of antennas of the otherwireless device; determine a phase correction based a comparison betweenthe first and second symbols; correct a phase and an amplitude of afourth symbol from a second plurality of antennas of the other wirelessdevice using the phase correction to produce a corrected symbol, thefirst and second plurality of antennas being different sets of antennas;and estimate an Angle of Departure (AoD) of the fourth symbol based onthe corrected symbol, wherein: the first and second symbols are disposedin a packet, the packet comprises a header and a plurality of symbolsthereafter, the plurality of symbols comprises pairs of symbolsseparated by a switching period during which signals received from theother wireless device are ignored, and the first and second symbols aredisposed in different packets, each packet comprises a header and a pairof symbols comprising a correction symbol and an AoD symbol, thecorrection symbol disposed before the AoD symbol, the first and secondsymbols being the correction symbols and the third and fourth symbolsbeing the AoD symbols.
 2. The apparatus of claim 1, further comprising:one or more antennas arranged to receive the symbols from the otherwireless device.
 3. An apparatus of a station (STA), the apparatuscomprising: a memory; and processing circuitry arranged to: decode afirst and second symbol from a first antenna of another wireless device;decode a third symbol from a first plurality of antennas of the otherwireless device; determine a phase correction based a comparison betweenthe first and second symbols, the first and second symbol received froma first antenna on a first set of tones and the first and second symbolreceived from a second antenna on a second set of tones different fromthe first set of tones; correct a phase of a fourth symbol from a secondplurality of antennas of the other wireless device using the phasecorrection to produce a corrected symbol, the first and second pluralityof antennas being different sets of antennas; and estimate an Angle ofDeparture (AoD) of the fourth symbol based on the corrected symbol. 4.The apparatus of claim 3, further comprising: one or more antennasarranged to receive the symbols from the other wireless device.
 5. Anapparatus of a wireless device, the apparatus comprising: a transceiver;and processing circuitry arranged to: cause the transceiver to transmit,to a station (STA) through use of a first antenna, a header and a firstsymbol; switch transmitter chains between a first set of antennas and asecond set of antennas after transmission of the first symbol, a numberof transmitter chains being smaller than a number of antennas; after theswitch, cause the transceiver to transmit, to the STA through use of thefirst antenna, another first symbol; cause the transmitter to transmit asecond symbol after both the first symbol and the other first symbol,the second symbol transmitted after the first symbol transmitted by thefirst set of antennas and the second symbol transmitted after the secondsymbol transmitted by the second set of antennas, the first and secondset of antennas comprising the first antenna; cause the transceiver toreceive location information from the STA, the location informationbased on an angle of departure (AoD) estimate dependent on use of thefirst symbol and the other first symbol to correct for a phase andamplitude variation caused by the switch; and cause the transmitter totransmit at least one of: a first packet comprising the header and afirst pair of symbols comprising the first symbol and one of the secondsymbols immediately after the first symbol, and a second packetcomprising the header and a second pair of symbols comprising the otherfirst symbol and another of the second symbols immediately after theother first symbol, or the first symbol from the first antenna on afirst set of tones and the other first symbol from the first antenna onthe first set of tones, and the other first symbol from a second antennaon a second set of tones and the other first symbol from the secondantenna on the second set of tones.
 6. The apparatus of claim 5, whereinthe processing circuitry is further arranged to: avoid transmissionduring the switch.
 7. The apparatus of claim 5, wherein the processingcircuitry is further arranged to: during the switch, cause thetransmitter to transmit a carrier wave and avoid transmission of asymbol.
 8. The apparatus of claim 5, wherein: the first and second pairof symbols are separated by a switching period during which thetransmitter chains are switched between the first and second sets ofantennas.
 9. The apparatus of claim 5, wherein the processing circuitryis further arranged to: cause the transmitter to transmit: a firstpacket comprising the header and a first pair of symbols comprising thefirst symbol and one of the second symbols immediately after the firstsymbol, and a second packet comprising the header and a second pair ofsymbols comprising the other first symbol and another of the secondsymbols immediately after the other first symbol.
 10. The apparatus ofclaim 5, wherein: transmission of the first symbol and the other firstsymbol is limited to the first antenna.
 11. The apparatus of claim 5,wherein the processing circuitry is further arranged to: cause thetransmitter to transmit: the first symbol from the first antenna on afirst set of tones and the other first symbol from the first antenna onthe first set of tones, and the other first symbol from a second antennaon a second set of tones and the other first symbol from the secondantenna on the second set of tones.
 12. The apparatus of claim 5,wherein the processing circuitry is further arranged to: transmit, priorto transmission of the header and first symbol, an announcement frame,the announcement frame comprising packet information comprising a numberof symbols between adjacent switches of the transceiver chain, a numberof symbols over which a particular switch occurs, and a codebook thatmaps tones in each symbol to respective physical angles.
 13. Theapparatus of claim 5, wherein: wherein the wireless device is an accesspoint (AP).
 14. A non-transitory computer-readable storage medium thatstores instructions for execution by one or more processors of a station(STA), the one or more processors to configure the STA to: decode a pairof comparison symbols from a first antenna of an access point (AP);decode a first and second Angle of Departure (AoD) symbol respectivelyfrom a first and second set of antennas, wherein the first and secondset of antennas comprise different antennas that comprise the firstantenna; determine a phase and amplitude correction based on a phase andamplitude change between the first and second comparison symbols; andcorrect a phase and amplitude of the second AoD symbol from the secondset of antennas through use of the phase and amplitude correction toproduce a corrected AoD symbol for the second set of antennas, whereinthe first comparison symbol and first AoD symbol are disposed in a firstpacket that comprises a first header, and the second comparison symboland second AoD symbol are disposed in a second packet that comprises asecond header.
 15. The medium of claim 14, wherein: the first packetcomprising the first comparison symbol and first AoD symbol separatedfrom the second comparison symbol and second AoD symbol by a periodduring which signals from the AP are ignored.
 16. The medium of claim14, wherein the one or more processors further configure the STA to:decode an announcement frame prior to reception of the first comparisonsymbol, the announcement frame comprising packet information comprisinga number of symbols in each set of symbols comprising a comparisonsymbol and an AoD symbol, a number of symbols between adjacent sets, anda codebook that maps tones in each symbol to respective physical angles.